Quantcast Vertical Backbone Physical Support Structure

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MIL-HDBK-1012/3
empty duct.  It will twist and preclude further use of the duct.
Optimum fill ratio may be obtained by pulling three innerducts
initially and leaving two empty with pull wire installed in each.
A quadduct of uniconstruction duct may be substituted as
appropriate.
1.8.3
Vertical Backbone Physical Support Structure.  The
vertical backbone physical support structure provides the means
for routing backbone cables through a multistory building.  Once
the transmission media is selected, the RCDD must select an
appropriately constructed cable to meet Federal and local fire
codes.  It is strongly recommended that new construction efforts
incorporate telecommunication closets directly above each other
to facilitate the most direct routing of vertical backbone cables
and eliminate the need for conduit.  The routing of vertical
cables should not interfere with the installation of distribution
backboards or equipment.  Vertical backbone cable should not be
routed through elevator shafts.  It is recommended that vertical
backbone cable not be routed through other building shafts which
preclude direct access to the cable.  If telecommunications
closets on adjoining floors are not vertically aligned,
horizontal routing will be required to interconnect them.  A
minimum of three 103 mm (4 in.) EMT conduits shall be provided as
a cable pathway in accordance with EIA/TIA 569.  Vertical access
through floors and ceilings shall be accomplished by installing
103 mm(4 in.) conduit sleeves or cut slots.  Conduit sleeves
should, as a minimum, extend 1 in. above and below the floor and
ceiling level.  Conduits, vertical sleeves, and slots shall be
firestopped in accordance with local building codes, American
Society for Testing and Materials (ASTM) E814, Fire Tests of
Through-Penetration Fire Stops, Underwriters' Laboratories Inc.
(UL) 1479, Safety Fire Tests of Through-Penetration Firestops,
and NFPA 70.  The BICSI Manual, Telecommunications Cable and
Pathway Design Parameters and Installation Practices and EIA/TIA
569 provide recommended sleeve quantities and slot sizes based on
serviceable square footage of the building.  These requirements
are reiterated in Example Five.  After selection of cable type,
sizing, and routing has been accomplished, the RCDD must
determine the best method of securing the backbone cable.  Again,
because there is a wide variety of available backbone cables, a
variety of methods is necessary and acceptable for securing them.
When determining the best method for securing a vertical cable,
the RCDD must consider the following factors:
a)
Foot/pound and total weight of the cable;
b)
Shear strength characteristics of the cable sheath;
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